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6. If [tex]\({ }^{12} C_2={ }^{2n} C_1\)[/tex], find [tex]\(n\)[/tex].

Hint:
[tex]\[
\frac{12 \cdot 11}{2 \times 1} = \frac{2n(2n-1)(2n-2)}{3 \times 2 \times 1}
\quad \Rightarrow \quad 18 \cdot (n-1) = (2n-1) \cdot 2(n-1)
\][/tex]

Sagot :

Sure, let's solve the given question step-by-step.

Given: [tex]\( 12 \cdot {}^4C_2 = {}^{2n}C_1 \)[/tex]

Recall the combination formula:
[tex]\[ {}^nC_r = \frac{n!}{r!(n-r)!} \][/tex]

First, let's compute both combinations involved in the problem:

1. For [tex]\( {}^4C_2 \)[/tex]:
[tex]\[ {}^4C_2 = \frac{4!}{2!(4-2)!} = \frac{4 \cdot 3 \cdot 2 \cdot 1}{(2 \cdot 1) \cdot (2 \cdot 1)} = \frac{24}{4} = 6 \][/tex]

2. For [tex]\( {}^{2n}C_1 \)[/tex]:
[tex]\[ {}^{2n}C_1 = \frac{(2n)!}{1!(2n-1)!} = \frac{2n}{1} = 2n \][/tex]

Substitute these results into the given equation:
[tex]\[ 12 \cdot 6 = 2n \][/tex]

Simplify:
[tex]\[ 72 = 2n \][/tex]

Solve for [tex]\( n \)[/tex]:
[tex]\[ 2n = 72 \implies n = \frac{72}{2} = 36 \][/tex]

Therefore, the value of [tex]\( n \)[/tex] is:
[tex]\[ \boxed{36} \][/tex]